This episode features the first appearance of Mark Lenard, as Spock's father Sarek. Mark Lennard is also the only actor in Trek history to have played a Romulan, a Klingon and a Vulcan.

"On Vulcan, the teddy bears are alive. And they have six-inch fangs." - Spock to McCoy.

This is the first episode to feature both the Tellarites and the Andorians. Both would later be identified as two of the founding members of the Federation.

Ambassador Sarek and Amanda arrive on board by shuttlecraft - this is because the episode spent so much on depicting all the various aliens on board the ship that there was no money left over for a transporter effect sequence to be filmed. By using the shuttle, they were able to show their arrival almost entirely using stock footage at zero cost.

Spock's decision to join Starfleet rather than attend the Vulcan Science Academy is seen in the 2009 Star Trek movie. In that, the decision is prompted by head of the VSA admission board commenting that Spock was being offered a position as his scores were sufficient to overcome his disadvantage of having a Human mother; Spock responds to the slight against his mother by refusing the offer, the first person ever to do so. Screenwriter Roberto Orci has stated that although the movie takes place in an altered timeline, this is how it played out in the original timeline too.

Manny Coto wanted to have the short, golden-skinned species from this episode appear in the Enterprise episode "Terra Prime". He named them Ithenites, a name Daniels mentioned in "Azati Prime". Unfortunately it proved to be too expensive.

D.C. Fontana regards this as her favorite of all the Star Trek episodes she wrote.

Plotline

The Enterprise is transporting a number of Federation ambassadors to the planet Babel, where a conference will debate the admission of the Coridan system to the Federation. Coridan is a major source of dilithium crystals, but mining rights on the planet are disputed by various groups and many appear to have a vested interest in preventing membership.

Kirk welcomes the Vulcan Ambassador, Sarek, on board along with his human wife Amanda. Kirk is surprised to learn that Sarek and Amanda are none other than Spock's parents, especially given that Sarek states that he prefers to tour the ship in the company of some other officer - clearly there is more than a little coldness and even animosity between Spock and his father.

At a social gathering the Tellarite Ambassador, Gav, demands to know Sarek's position on the Coridan issue. Sarek states that he favours membership, to the Tellarite's annoyance. When Sarek implies that the Tellarites want to keep Coridan out of the Federation so they can continue illegal mining activities on the surface, Gav is so furious that Kirk has to intervene to prevent a fight.

Shortly thereafter, Ambassador Gav is found murdered - his neck broken by a Vulcan method called Tal-Shaya. Spock states that his father is perfectly capable of killing, if he believed it necessary to do so. Kirk goes to question Sarek about the incident, but during the questioning Sarek practically collapses in pain. McCoy diagnoses a cardivascular condition and puts Sarek in sickbay. Meanwhile on the bridge, Uhura detects an encoded transmission beamed from the Enterprise, apparently directed at a ship at the extreme edge of sensor range. They manage some scans of the ship, finding that it has an tri-titanium hull. This apparently rules out Romulan, Federation, or Klingon origin, and makes even the neutral planets unlikely. As they scan, the ship transmits a coded burst towards them - apparently intended to be picked up by somebody aboard.

In sickbay, McCoy has determined that Sarek is suffering from a malfunctioning heart valve. Sarek states that he has had several previous attacks, including one during Gav's murder - although he has no witnesses, he states that this left him completely incapacitated and thus unable to act against Gav. McCoy has a potential solution, an operation to repair the valve, but the procedure would require a massive amount of Vulcan blood - far more than the Enterprise has in stock. Although there are potential donors on board, Sarek's T-negative blood type makes them incompatible. Spock points out that his own blood type is T-negative, and once the human factors are filtered out it should be just possible to perform the procedure.

Meanwhile a member of the Andorian delegation, Thelev, attacks Captain Kirk. Kirk wins the fight but is stabbed in the process. He is rushed to sickbay as Thelev is confined to the brig. With Kirk incapacitated Spock is left in command of the ship - and as a result, flatly declines to submit himself to act as donor for Sarek as it now conflicts with his duties. Even an impassioned plea from his mother leaves him unmoved.

On hearing this, Kirk asks McCoy to patch him up sufficiently to pretend that he is well for a few minutes, so that he can relieve Spock and order him to sickbay; Kirk then plans to turn over command to another officer and go back to sickbay himself. Uhura picks up another communications burst, this one directed at the ship's brig. Thelev is searched, and a communications device discovered in his antennae; he is not an Andorian at all, but another species surgically altered.

The unidentified ship closes in and attacks, moving at extreme speeds - Warp 10, too fast for the Enterprise to be able to target it. Kirk remains on the bridge to handle the attack despite his wounds, ordering Thelev nrought to the bridge for questioning. He refuses to give any information, so Kirk begins to shut down systems on the Enterprise, making it appear as if the attacks are damaging the ship and leaving it helpless. The attacker moves in, slowing down as it comes to make the kill - and Kirk unleashes a phaser barrage that cripples the enemy ship. The disabled warship self-destructs, and Thelev reveals that he has taken a delayed action poison which kills him.

Kirk returns to sickbay and finds Spock and Sarek both alive and well. Spock speculates that both the ship and Thelev were of Orion origin; the ship was always on a one way suicide mission, which meant it needed to hold nothing back for the trip back home - the reason it was able to fly so fast. The Orions intended to sow distrust among the Federation members and thus allow the Orions to continue with their raiding of Coridan for dilithium - and indeed, if a Federation civil war had resulted, boost their profits still further by selling to both sides.

Spock and Sarek seem to have warmed considerably in relation to one another, which pleases Amanda greatly - though she is frustrated when both insist they are merely being wholly logical. Spock comments on her temper, wondering why Sarek marries her - to which the Ambassador states only that it seemed like the logical thing to do. McCoy uses his medical authority to order everyone to quiet down, and gloatingly observes that for once, he got the last word.

Analysis

A fascinating episode this, always strongest when it is dealing with Spock and his parents. You get a lot of character development here; the idea of the rift between father and son is nothing new, but it's done well here because it's not overplayed or reduced to simple right and wrong issues. Sarek isn't being terribly unreasonable here, from his point of view Spock has spurned a great opportunity and instead joined an organisation that Vulcans in general seem to look on with more than a little distaste. And Spock isn't acting out or rebelling just to rebel, he's merely chosen his own course in life to suit his own goals. Both are stuck in the situation, but you can sympathise with either one - and that's especially true given the excellent performances by both actors. Nimoy's Spock is an iconic character, but Mark Lenard truly does stand toe to toe with him here and give us another really memorable Vulcan. And we shouldn't overlook Amanda; it's interesting after all McCoy's talk of how superior Human emotions are (McCoy is actually quite a racist, if you think about it) to see Amanda who has, at least to some extent, "gone native" on Vulcan, and openly states that their way is better than ours, at least in some respects. Yet she isn't trying to BE a Vulcan as such - she isn't trying to be unemotional herself, as we see in her interactions with Spock. I guess she might say it would be illogical for her to give up on her humanity completely!

It's also nice to see all the alien races on board, and a story that focuses on Federation politics. In Star Trek it's very often simply assumed that the Federation will automatically do what is "right", with no regards to cost, politics, difficulty or anything else. Starfleet officers routinely decide the fate of whole planets, and they rarely have to check back in with home to see if that's actually what the Federation wants them to do. Here, though, we see that the Federation has many factions and that some of them are positively aggressive towards others. The prospect of a Federation civil war is raised as a distinct possibility. It all goes to a model of the Federation that is closer to the UN model than the kind of thing we see in TNG, where the Federation seems more like the USA, with member planets being like individual states.